The present invention relates to on the one hand a method of determining where the cylinders of a multiple cylinder engine are operating during their operating cycle and for adjusting the cycle positions of the cylinders and on the other hand to an arrangement for the determining and adjusting.
In internal combustion engines of the four-stroke type, the camshaft rotates at half the crankshaft speed, as a result of which the rotary position of the camshaft at any moment clearly indicates where in its operating cycle, or in which cycle position, a given cylinder is located. By studying the rotary position of the camshaft, it is therefore possible to determine whether the current position of the piston in a cylinder is to be assigned to the first or the second crankshaft revolution in each operating cycle of the cylinder. By means of camshaft sensors, it is thus possible to provide, for example, an electronic control unit for a fuel injection system with reliable information about the cycle position in a cylinder, so that fuel injection can always take place at the correct time.
However, such camshaft sensors are relatively difficult to install and to make sufficiently robust, for which reason it would be desirable for it to be possible to utilize simpler systems but still achieve good precision and reliability. In electronic fuel injection systems, the failure of such a camshaft sensor can result in functional problems, as the possibility of determining the current cycle position is thus lost.
It has also been found to be difficult to use only flywheel sensors instead, as uncertainty arises about which of two crankshaft revolutions the engine is in at the time. Another problem in this context is that an electronic control unit, for example in connection with being started or after a programming change or the like, cannot retain stored information about the position in which the crankshaft last stopped, but has to be synchronized with the engine again. Furthermore, the crankshaft may, since the engine stopped, have been rotated as a result of the vehicle having been moved with a gear engaged. Such circumstances may result in the control unit misinterpreting the situation and operating in an incorrect cycle position, with attendant operating problems.
Against this background, a requirement exists for improved solutions within this field.
An object of the invention is to make it possible, without recourse to camshaft sensors, to determine reliably the cycle position of a cylinder in a multiple cylinder four-stroke engine. Another object is to produce a simple and safe solution.
These objects are achieved according to the invention by means of on the one hand a method for superimposing interference oscillations on the engine flywheel and then determining if the phase of the interference oscillations is in a predetermined relationship to the phase of the resultant oscillations on the flywheel caused by the ignition impulses and the superimposed interference oscillations; and adjusting the engine cycle position, i.e. where in the cycle fuel is injected to each of the cylinders, to attain the predetermined relationship of the phases, having on the other hand an arrangement having a control unit which applies the interference oscillations, senses the rotation angle of the flywheel, determines if the cycle position is correct or not, and causes corrections of an incorrect cycle position to provide the predetermined phase relationship.
By, according to the invention, dispensing with camshaft sensors and using only a flywheel sensor (crankshaft sensor), a simpler, more robust sensor arrangement is obtained. In order for it then to be possible to determine, on starting, in which crankshaft revolution of the two revolutions of an operating cycle a cylinder is located, the flywheel is subjected to an interference oscillation in addition to the ordinary ignition pulse oscillation. The superimposed interference oscillation can be determined from the resultant oscillation, and, after comparison of phase positions of the superimposed interference oscillation and the interference oscillation, it is possible to establish which of the two crankshaft revolutions is correct for the cylinder. An electronic control unit which detects that the cycle position is incorrect is initiated to correct its cycle position by jumping the necessary number of steps in the ignition sequence of the engine, so that the correct cycle position is reached. A suitable interference oscillation is brought about by temporarily changing the fuel supply to the cylinders of the engine so that some cylinders receive more fuel and others receive less, according to a selected pattern.
By ensuring that a control unit can be set correctly on each starting operation, it is possible to use various types of control units with differing characteristics together with the engine with high reliability. The superimposed interference oscillation can be made virtually imperceptible for the driver of the vehicle by virtue of its frequency harmonizing with the ordinary oscillation and by virtue of the procedure being effected briefly at the beginning of the starting operation.
The arrangement produced according to the invention can be constructed using simple components and can therefore be made simple and robust.
Further features and advantages of the invention emerge from the description below.
The invention is described in greater detail below by means of illustrative embodiments shown in the accompanying drawing.